Method for changing operating mode of wireless lan system and wireless lan system

ABSTRACT

An operating mode change method of a wireless local area network (WLAN) system according to an exemplary embodiment includes transmitting, by a station (STA) to an access point (AP), an operating mode change request frame comprising at least one of information on a change of a traffic indication map (TIM) mode, a request for a change of a power save parameter, and information on a change of a service type of the STA, receiving, from the AP, an operating mode change response frame comprising at least one of a TIM mode allowed by the AP, a reallocated association identification (AID), and information on a changed power save parameter, and performing at least one of the change of the TIM mode and the change of the power save parameter based on the information included in the operating mode change response frame.

TECHNICAL FIELD

The present invention relates to a wireless local area network (WLAN)system and an operating mode change method of the WLAN system.

BACKGROUND ART

Wireless local area network (WLAN) technology is developing in threedirections.

First, a 60-gigahertz (GHz) band and a 5-GHz band are used in a WLAN inorder to enhance a transfer rate. Second, a frequency band of less than1 GHz is used for a wireless wide area network (WWAN) uses to expand acoverage thereof as compared with conventional WLAN technology. Third, atechnique of reducing a link setup time of a WLAN system is adopted.

A WWAN is required to accommodate a remarkably larger number of stations(STAs) than an established WLAN.

Further, WWAN technology may need to support STAs with various servicetypes, such as offloading terminals and sensor terminals, traffic types,and power saving demands.

Therefore, a WWAN system is advancing to reduce collisions in channelaccess and to achieve efficient power saving by grouping a plurality ofSTAs.

DISCLOSURE OF INVENTION Technical Goals

An aspect of the present invention is to provide an operating modechange method of conducting proper allocation of AIDs to a various typesof stations (STAs), efficient STA group management, channel access,power saving and sector allocation so as to simultaneously support theSTAs in a wireless local area network (WLAN) system, and a WLAN systemusing the same.

Further, another aspect of the present invention is to provide a framestructure and a communication method for exchanging various parametersto efficiently change an operating mode.

In addition, still another aspect of the present invention is to providea method of enabling an operating mode change including a TIM/non-TIMmode change, a change of a service type of an STA and a BSS mode change,AID reallocation, an STA group change and a power save parameter.

Technical Solutions

According to an aspect of the present invention, there is provided anoperating mode change method of a wireless local area network (WLAN)system, the method including transmitting, by a station (STA) to anaccess point (AP), an operating mode notification frame includinginformation on a used bandwidth, information on a number of spatialstreams, and information on a change of a traffic indication map (TIM)mode, receiving, from the AP, an operating mode change response frameincluding information on a reallocated association identification (AID)of the STA, and performing the change of the TIM mode based on theinformation included in the operating mode change response frame.

According to another aspect of the present invention, there is alsoprovided an operating mode change method of a WLAN system, the methodincluding transmitting, by a STA to an AP, an operating mode changerequest frame including at least one of information on a change of a TIMmode, a request for a change of a power save parameter, and informationon a change of a service type of the STA, receiving, from the AP, anoperating mode change response frame including at least one of a TIMmode allowed by the AP, a reallocated AID, and information on a changedpower save parameter, and performing at least one of the change of theTIM mode and the change of the power save parameter based on theinformation included in the operating mode change response frame.

According to still another aspect of the present invention, there isalso provided an operating mode change method of a WLAN system, themethod including receiving, by an AP, an operating mode notificationframe including information on a bandwidth used by an STA, informationon a number of spatial streams, and information on a change of a TIMmode of the STA, determining whether to allow the change of the TIM modeof the STA, transmitting, to the STA, an operating mode change responseframe including information on a reallocated AID of the STA, andreceiving an acknowledgement (ACK) frame from the STA.

According to yet another aspect of the present invention, there is alsoprovided an operating mode change method of a WLAN system, the methodincluding receiving, by an AP, an operating mode change request frameincluding at least one of information on a change of a TIM mode of anSTA, a request for a change of a power save parameter, and informationon a change of a service type of the STA, determining whether to changethe TIM mode of the STA and whether to change the power save parameter,determining an STA group to which the STA belongs based on the TIM modeof the STA to be changed, a power save parameter of the STA that the APallows changing, and information on the service type of the STA andreallocating an AID based on a determination result, transmitting, tothe STA, an operating mode change response frame including at least oneinformation of a TIM mode allowed by the AP, the reallocated AID, andthe changed power save parameter, and receiving an ACK frame from theSTA.

According to further another aspect of the present invention, there isalso provided an STA of a WLAN system, the STA including a transmissionunit to transmit, to an AP, an operating mode notification frameincluding information on a used bandwidth, information on a number ofspatial streams, and information on a change of a TIM mode, a receptionunit to receive, from the AP, an operating mode change response frameincluding information on a reallocated AID of the STA, and a controllerto perform the change of the TIM mode based on the information includedin the operating mode change response frame.

According to still another aspect of the present invention, there isalso provided an STA of a WLAN system, the STA including a transmissionunit to transmit, to an AP, an operating mode change request frameincluding at least one of information on a change of a TIM mode of theSTA, a request for a change of a power save parameter, and informationon a change of a service type of the STA, a reception unit to receive,from the AP, an operating mode change response frame including at leastone of a TIM mode allowed by the AP, a reallocated AID, and informationon a changed power save parameter, and a controller to perform at leastone of the change of the TIM mode and the change of the power saveparameter based on the information included in the operating mode changeresponse frame.

According to yet another aspect of the present invention, there is alsoprovided an AP of a WLAN system, the AP including a reception unit toreceive an operating mode notification frame including information on abandwidth used by an STA, information on a number of spatial streams,and information on a change of a TIM mode of the STA, a controller todetermine whether to allow the change of the TIM mode of the STA, and atransmission unit to transmit, to the STA, an operating mode changeresponse frame including information on a reallocated AID of the STA.

According to still another aspect of the present invention, there isalso provided an AP of a WLAN system, the AP including a reception unitto receive an operating mode change request frame including at least oneof information on a change of a TIM mode of an STA, a request for achange of a power save parameter, and information on a change of aservice type of the STA, a controller to determine whether to change theTIM mode of the STA and whether to change the power save parameter, todetermine an STA group to which the STA belongs based on the TIM mode ofthe STA to be changed, a power save parameter of the STA that the APallows changing, and information on the service type of the STA and toreallocate an AID based on a determination result, and a transmissionunit to transmit, to the STA, an operating mode change response frameincluding at least one information of a TIM mode allowed by the AP, thereallocated AID, and the changed power save parameter.

Advantageous Effects

An operating mode change for efficient STA group management, channelaccess, power saving and sector allocation may be achieved in a wirelesslocal area network (WLAN) system.

Further, an efficient operating mode change may be achieved through aframe structure and a communication method for exchanging variousparameters to efficiently change an operating mode.

In addition, an operating mode change including a TIM/non-TIM modechange, a change of a service type of an STA and a BSS mode change, AIDreallocation, an STA group change and a power save parameter change maybe achieved.

Thus, exemplary embodiments of the present invention enable a basicservice set (BSS) of a wireless wide area network (WWAN) to beefficiently managed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a multi-bandwidth of a wireless wide area network(WWAN) system.

FIG. 2 illustrates an operating mode change method of an access point(AP) according to an exemplary embodiment.

FIG. 3 illustrates an operating mode change method of a station (STA)according to an exemplary embodiment.

FIG. 4 illustrates definitions of action field values of a wirelesslocal area network (WLAN) system according to an exemplary embodiment.

FIG. 5 illustrates an action field format of an operating modenotification frame according to an exemplary embodiment.

FIG. 6 illustrates a format of an operating mode notification elementaccording to an exemplary embodiment.

FIG. 7 illustrates a configuration of an action field format of anoperating mode change request frame according to an exemplaryembodiment.

FIG. 8 illustrates a configuration of an operating mode change requestfield according to an exemplary embodiment.

FIG. 9 illustrates various configurations of an operating mode changerequest frame according to an exemplary embodiment.

FIG. 10 illustrates a use of an Access Policy subfield of FIG. 9.

FIG. 11 illustrates another use of the Access Policy subfield of FIG. 9.

FIG. 12 illustrates a TSPEC element in accordance with relatedtechnology.

FIG. 13 illustrates a configuration of a TS Info field of FIG. 12.

FIG. 14 illustrates a use of a medium access preference element of FIG.9.

FIG. 15 illustrates an action field format of an operating mode changeresponse frame according to an exemplary embodiment.

FIG. 16 illustrates a configuration of an operation mode change responsefield according to an exemplary embodiment.

FIG. 17 illustrates a configuration of an operation mode change responsefield according to another exemplary embodiment.

FIG. 18 illustrates a configuration of a medium access parameter elementaccording to an exemplary embodiment.

FIG. 19 illustrates a configuration of a medium access parameter elementaccording to another exemplary embodiment.

FIG. 20 illustrates a schematic configuration of an AP according to anexemplary embodiment.

FIG. 21 illustrates a schematic configuration of an STA according to anexemplary embodiment.

FIGS. 22 to 28 illustrate various examples of operation mode changemethods of an AP or a STA.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, exemplary embodiments of the present invention aredescribed in detail with reference to the accompanying drawings.

FIG. 1 illustrates a multi-bandwidth of a wireless wide area network(WWAN) system.

A WWAN system, for example, a wireless local area network (WLAN) systemdefined in an Institute of Electrical and Electronics Engineers (IEEE)802.11ah standard, may support a multi-bandwidth. The multi-bandwidthmay include a first bandwidth with a lowest signal-to-noise ratio (SNR)and a second bandwidth twice larger than the first bandwidth. Here, thefirst bandwidth is 1 megahertz (MHz).

Referring to FIG. 1, the multi-bandwidth may include a 1-MHz bandwidth110, a 2-MHz bandwidth 120, a 4-MHz bandwidth 130, an 8-MHz bandwidth140 and a 16-MHz bandwidth 150. The WWAN system may have a frequencyband of 1 gigahertz (GHz) or less.

Thus, the multi-bandwidth may be expressed as including 1 MHz, 2 MHz, 4MHz, 8 MHz, and 16 MHz.

Thus, in FIG. 1, a lower frequency 161 may range from 700 to 920 MHz,and an upper frequency 163 may range from 750 to 930 MHz.

As shown in FIG. 1, the 1-MHz bandwidth 110 may be allocated for anentire channel, while the other bandwidths 120, 130, 140, and 150 may beallocated for only part of the entire channel.

For example, the 16-MHz bandwidth 150 may be allocated between areference numeral 163 of FIG. 1 and the upper frequency 163. Referringto FIG. 1, the 2-MHz bandwidth 120 may be allocated eight channels, the4-MHz bandwidth 130 may be allocated four channels, and the 8-MHzbandwidth 130 may be allocated two channels. However, channel allocationshown in FIG. 1 is provided for illustrative purposes only, and a numberof channels and a frequency band may be configured in various methods.

A transmission mode using the 1-MHz bandwidth 110 may be defined as a1-MHz mode, while a transmission mode using the 2-MHz bandwidth 120 maybe defined as a 2-MHz mode.

FIG. 2 illustrates an operating mode change method of an access point(AP) according to an exemplary embodiment. FIG. 3 illustrates anoperating mode change method of a station (STA) according to anexemplary embodiment.

Referring to FIG. 2, an AP 210 of the WLAN system may notify an STA 220of a change of an operating mode in operation 211.

Here, the AP 210 may broadcast an operating mode notification frame,thereby notifying the STA 220 of the change of the operating mode of theAP 210.

The AP 210 may change a bandwidth used by the AP 210, a number ofspatial streams and a basic service set (BSS) mode. Here, the operatingmode notification frame may include information on at least one of abandwidth changed by the AP for use, a number of spatial streams, achange of the BSS mode, Rx Nss and an Rx Nss type. The Rx Nss and Rx Nsstype will be described.

The STA 220 may transmit an acknowledgement (ACK) to the AP 210 inoperation 221.

Referring to FIG. 3, the station 320 transmits an operating modenotification frame including information on a change of a usedbandwidth, information on a change of a traffic indication map (TIM)mode, and information on a change of a number of spatial streams, forexample, Rx Nss and Rx Nss type, to the AP in operation 321.

Here, the station 320 may conduct unicast of the operating modenotification frame. The information included in the operating modenotification frame may be added or changed variously.

The AP 310 receives the operating mode notification frame including theinformation on the change of the station used bandwidth, the informationon the change of the TIM mode, and the information on a change of thenumber of spatial streams, for example, Rx Nss and Rx Nss type, inoperation 321.

The AP 310 may transmit an ACK to the station 320 in operation 311.

The AP 310 may determine whether to allow the change of the TIM mode orthe SAT 320, reallocate the STA to a different group for efficientstation grouping in the BSS, and accordingly reallocate an associationidentification (AID) to the STA. In operation 313, the AP 310 transmitsan operating mode change response frame including changed operatinginformation of the STA, such as the reallocated AID of the STA 320.

When the change of the TIM mode is approved by the AP 310, the operatingmode change response frame may further include group change informationdue to the change of the TIM mode. Further, when the STA is reallocatedto a different group, the operating mode change response frame mayfurther include power save parameters of the STA changed accordingly,such as a listen interval, a sleep duration, or a wakeup interval.

Here, the TIM mode may include an operation mode of not verifying theTIM transmitted from the AP and an operation mode of verifying the TIMtransmitted from the AP at a preset time.

The STA 320 receives the operating mode change response frame from theAP 310 and changes an operation mode, for example, the TIM mode, a sleepduration or a wakeup interval, based on the information included in theoperating mode change response frame.

Although not shown in FIG. 3, before transmitting the operating modenotification frame to the AP 310 or after changing the TIM mode,receiving an operating mode notification frame of the AP 310 includinginformation on a change of an operating mode of the AP 310 from the AP310 may be further included.

Here, the operating mode notification frame of the AP 310 may includeinformation on whether the AP supports all types of stations, supportsonly a sensor node, or supports only an offloading device.

Meanwhile, as an alternatively method of requesting an operating modechange to the AP, the STA 320 may transmit an operating mode changerequest frame including information on the change of the TIM mode andinformation on a request for a change of a power save parameter to theAP 310 in operation 321.

The operating mode change request frame may further include at least oneof information on a request for allocation of a sector supported by theAP 310, information on a traffic type of the STA and information on aservice type that the station wishes to change.

The AP 310 determines whether to change the TIM mode of the STA andwhether to change the power save parameter, determines a changed STAgroup to which the STA belongs based on a changed TIM mode of the STAand a changed power save parameter of the STA that the AP allows,traffic information of the STA or information on a changed service type,and accordingly reallocates an AID to the STA. In operation 313, the AP310 may transmit an operating mode change response frame including atleast one of the reallocated AID of the station 320 and the changedpower save parameters of the STA, such as the listen interval, the sleepduration or the wakeup interval, to the station 320.

The operating mode change response frame may further include informationon a TIM mode allowed by the AP 310, group change information due to thechange of the TIM mode and a slot allocated to the STA 320.

The STA 320 may change at least one of the TIM mode and the power saveparameters including the sleep duration and the wake up interval basedon the information included in the operating mode change response frame.

The information on the request for the change of the power saveparameter may include at least one of information on a request for achange of the listen interval of the STA 320, information on a requestfor a change of a maximum idle period, and information on a request fora change of the sleep duration, such as a wireless network management(WNM) sleep interval or the wakeup interval of the STA.

Although not shown in FIG. 3, before the STA 320 transmits the operatingmode change request frame to the AP 310 or after the STA 320 performsthe change, receiving an operating mode change response frame includinginformation on a change of an operating mode of the AP from the AP 310may be further included.

The AP may transmit an operating mode response to STAs as necessary inoperation of a BSS of the AP without the STA explicitly requesting achange of the operating mode (if unsolicited), so that the STAs maychange operation modes of the STAs. For example, when regrouping of STAsin the BSS is needed as a greater number of new STAs are associated withthe AP or a great number of STAs leave the BSS, the STAs may bereallocated AIDs and relevant parameters including power save parametersmay be changed if necessary. Further, STAs performing a sectorizationfunction may be regrouped, and accordingly a sectorization group may bereallocated for STAs and a specific sector transmission duration may bechanged. Without a request for a change of an operating mode from an STA(if un solicited), the AP may transmit an operating mode response to theSTAs as necessary in operation of the BSS of the AP to send informationon the reallocated AIDs, a changed power save parameter, a reallocatedsector group of STAs due to a sector group change and a relevant sectortransmission duration to the STAs, so that the STAs may change theoperations modes thereof.

In the process of FIG. 3, the STA 320 may change the used bandwidth, thenumber of spatial streams and the TIM operation mode by transmitting theoperating mode notification frame or an operating mode notificationinformation element to the AP.

When the STA requests the change of the TIM operation mode or the changeof the power save parameter or when the traffic type or service type ofthe STA is changed, the AP 310 determines a changed STA group to whichthe STA belongs based on a changed TIM mode of the STA and a changedpower save parameter of the STA that the AP allows, and trafficinformation or information on a changed service type of the STA,reallocates an AID to the STA accordingly, and notifies the STA 320 ofan operating mode change response frame including information on thereallocated AID and the changed power save parameter. Further, when thegroup of the STA 320 is changed or a slot allocated to the STA 320 foruse is changed, the AP 310 may notify the STA 320 of an STA group ID anda slot number using the operating mode change response frame. Inaddition, when the AP changes the sector group of the STA, the AP maynotify the STA 320 of a reallocated sector group, such as a sector ID ora group ID, and a sector transmission duration using the operating modechange response frame.

When slotted channel access operates in a manner of implicitlydetermining the STA group ID when the AID of the STA 320 is determinedin the BSS and of reporting a slot number separately, the STA group IDand the slot number may not be included in the operating mode changeresponse frame.

When the STA requests the change of the TIM mode by transmitting theoperating mode notification frame to the AP, the AP 310 transmits theoperating mode change response frame to the STA 320 to notify the STA ofthe operating mode of the STA changed by the AP when the change of theTIM mode is allowed.

The AP may reallocate a group for the STA based on the changed TIM mode,reallocate an AID to the STA accordingly, change a power save parameterof the STA if necessary, and notify the STA of operating modeinformation, such as the changed AID and the power save parameterthrough the operating mode change response frame. When the TIM operationmode is not changed, the AP 310 may not transmit the operating modechange response to the STA 320.

When the STA requests the change of the operation mode by transmittingthe operating mode change request frame to the AP, the AP 310 transmitsthe operating mode change response frame to the STA 320 to notify theSTA of the operating mode of the STA changed by the AP. The STA maynotify the AP of more detailed information, such as the power saveparameter, the service type or traffic type of the STA that the STAexplicitly wishes to change, when the operating mode change requestframe is transmitted to request the change of the operation mode thanwhen the operating mode notification frame is transmitted.

The AP 310 transmits the reallocated AID of the STA 320 and the powersave parameters, such as the listen interval of the STA 320 allowed bythe AP, the maximum idle period or the sleep duration including the WNMsleep interval or the wakeup interval of the STA, to the STA 320 whentransmitting the operating mode change response. In addition, when thechange of the TIM mode is allowed so that the STA operates in asectorization mode, the AP may further transmit operation modeinformation, for example, the reallocated sector group, such as thesector ID or group ID, and the sector transmission duration, to the STA320.

When the STA transmits the operating mode notification frame to the APto request the change of the TIM operation mode or when the STAtransmits the operating mode change request frame to the AP, the STA 320may need to receive the operating mode change response, verify thechange of the operation mode and then enter a sleep state.

When the AP 310 does not allow the change of the operation moderequested by the STA 320, the AP 310 may report through the operatingmode change response that the change is impossible.

For example, when the STA 320 wishes to change the TIM mode from non-TIMto TIM, the AP 310 may not allow the change. Here, the AP 310 mayrespond with the non-TIM mode through an operating mode change response,instead of the TIM mode requested by the STA 320.

The STA 320 may use an operating mode notification element included in abeacon frame, a probe response or an association response when the STA320 first enters the BSS and verifies the operation mode of the AP 310.

The STA may specify an operating mode desired by the STA, for example, aTIM mode, a desired channel bandwidth and a desired number of spatialstreams, in the operating mode notification element, includes theoperating mode notification element in an association request frame, andtransmit the association request frame to the AP when the STA isassociated with the AP. The AP 310 may verify the desired operating modeof the STA through the operating mode notification element included inthe association request. The AP 310 may reject the association of theSTA 320 when the AP 310 does not support the operating mode desired bythe STA 320, for example, a non-TIM operation.

The STA may notify the AP of the operating mode desired by the STA byincluding a medium access preference element, which will be mentioned,in the association request frame, in addition to the operating modenotification element. The medium access preference element is an elementincluding similar information to operation mode change information onthe STA included in the operating mode change request frame. When themedium access preference element is included in the association requestframe, the STA may notify the AP of an STA-desired TIM mode, power saveparameters including a sleep duration, such as a listen interval orwakeup interval, a traffic type or service type of the STA and a sectorID of a preferred sector at association time, and the AP may determinewhether to allow association of the STA based on the element and set upa mode of the STA at association time.

When the STA transmits mode setup information, such as the operatingmode notification element or the medium access preference element, tothe AP through the association request, the AP may include a mediumaccess parameter element, which will be described, as mode setupinformation on the STA in an association response frame for transmissionto the STA when transmitting an association response to the STA, so thatthe STA may set up an initial operating mode in the BSS. The mediumaccess parameter element is an element including similar information tooperation mode change information of the STA included in the operatingmode change response frame allowed by the AP. When the medium accessparameter element is included in the association response, the STA mayrecognize a TIM mode of the STA allowed by the AP at association time,an AID of the STA, power save parameters including a sleep duration,such as a listen interval or wakeup interval, an allocated sector groupof the STA, such as a sector ID or sector group ID, if the STA usessectorization, and duration information on a relevant sector andimmediately set up an operating mode at association time based on theelement.

The STA 320 may transmit information not only on the change of the TIMmode but also on a request for AID reallocation, a request for a changeof an STA group, a service type or traffic type of the STA, sectorallocation or sector reallocation to the AP 310 using the operating modechange request frame in operation 321.

The AP 310 may transmit a reallocated AID and information on a sectorgroup allocated for the STA, such as a sector ID or sector group ID, tothe STA 320 in operation 313. Here, when the STA 320 explicitly requestsa change of power save parameters including a sleep duration, such as alisten interval or wakeup interval, or when the AP determines that achange of power save parameters is needed based on the information onthe traffic type or service type of the STA and the information on therequest of the change of the TIM mode without an explicit request by theSTA, the AP 310 may transmit the power save parameters allocated by theAP including the sleep duration, such as the listen interval or wakeupinterval, to the STA 320 and the STA 320 may change the operating modeas far as the AP permits.

The AP 310 transmits the reallocated AID of the STA 320 and the powersave parameters, such as the listen interval of the STA 320 allowed bythe AP, the maximum idle period, the WNM sleep interval or the sleepduration including the wakeup interval of the STA, to the STA 320 whentransmitting the operating mode change response. Further, when thechange of the TIM mode is allowed so that the STA operates in asectorization mode, the AP may further transmit operation modeinformation, for example, the reallocated sector group, such as thesector ID or group ID, and the sector transmission duration, to the STA320.

Here, the STA 320 transmits the operating mode change request, receivesthe operating mode change response, verifies the changed operating modethereof, and then enters the sleep state.

When the AP 310 does not allow the power save parameters, such as thelisten interval, the maximum idle period, the WNM sleep interval or thesleep duration including the wakeup interval of the STA, and the sectorgroup as requested by the STA 320, the AP 310 may notify the STA 320 ofallowable power save parameters, such as a listen interval, a maximumidle period, a WNM sleep interval or a sleep duration including a wakeupinterval of the STA, and an allocated sector group through the operatingmode change response.

The STA 320 may change the operating mode using values allowed by the AP310.

The AP may transmit an operating mode response to STAs as necessary inoperation of a BSS of the AP without the STA explicitly requesting achange of the operating mode (if unsolicited), so that the STAs maychange operation modes of the STAs. For example, when regrouping of STAsin the BSS is needed as a greater number of new STAs are associated withthe AP or a great number of STAs leave the BSS, the STAs may bereallocated AIDs and relevant parameters including power save parametersmay be changed if necessary. Further, STAs performing a sectorizationfunction may be regrouped, and accordingly a sectorization group may bereallocated for STAs and a specific sector transmission duration may bechanged. Without a request for a change of an operating mode from an STA(if un solicited), the AP may transmit an operating mode response to theSTAs as necessary in operation of the BSS of the AP to send informationon the reallocated AIDs, a changed power save parameter, a reallocatedsector group of STAs due to a sector group change and a relevant sectortransmission duration to the STAs, so that the STAs may change theoperations modes thereof.

The operating mode change methods described in FIGS. 2 and 3 may beillustrated with reference to FIGS. 22 to 28.

FIG. 22 is an example illustrating that the AP reports a change of anoperating mode thereof using an AH operating mode notification frame.

FIG. 23 is an example illustrating that the AP notifies the STA of anAID, an STA group, slot allocation, and sector allocation using anoperating mode change response frame. Here, the operating mode changeresponse frame may be transmitted if necessary during an operation of aBSS of the AP without a request for a change of the operating mode fromthe STA.

FIG. 24 is an example illustrating that the AP notifies the STA of AIDallocation using an operating mode change response frame. Here, FIG. 24shows a method of implicitly determining an STA group ID when an AID ofthe STA is determined in a BSS and of reporting a slot numberseparately.

FIG. 25 is an example illustrating a change of an operation mode of theSTA using an operating mode notification frame. Here, an operating modechange response may be transmitted when the TIM Mode is changed.

FIG. 26 is another example illustrating a change of an operation mode ofthe STA using an operating mode notification frame. Here, an operatingmode change response is necessarily transmitted when the TIM mode ischanged.

FIG. 27 is an example illustrating that the STA changes an operationmode thereof using an operating mode change request frame and an AHoperating mode change response frame. Here, an operating mode changeresponse is always transmitted regardless of a change of the TIM mode.

FIG. 28 is another example illustrating that the STA changes anoperation mode thereof using an operating mode change request frame andan AH operating mode change response frame.

Hereinafter, various frames to be used for changing an operating modewill be described with reference to FIGS. 4 to 19.

FIG. 4 illustrates definitions of action field values of the WLAN systemaccording to an exemplary embodiment.

In the specification, a term including “AH” may be used to indicatetechnology applicable to an 802.11ah WLAN system.

For an operating mode change, an AH operating mode notification frame,an AH operating mode change request frame and an AH operating modechange response frame may be used.

The AH operating mode notification frame, the AH operating mode changerequest frame and the AH operating mode change response frame may bedefined as AH action field values in FIG. 4. Here, it is an illustrativeexample that a frame for changing the operating mode is defined as anaction frame, and a frame in a different form including similarinformation may be also used.

FIG. 5 illustrates an action field format of an operating modenotification frame according to an exemplary embodiment.

An operating mode notification frame and an operating mode notificationelement may be used to notify the STA of an operating channel width anda maximum number of spatial streams for reception. The WWAN system maysupport a non-TIM operation mode and also support a BSS mode formed ofsensor nodes only, a BSS mode formed of offloading devices only, and aBSS mode formed of combinations thereof.

The operating mode notification frame and the operating modenotification element may report the non-TIM operation mode and a BSSmode formed of specific STAs only, for example, the BSS mode formed ofsensor nodes only, the BSS mode formed of offloading devices only andthe BSS mode formed of combinations thereof, thereby supportingTIM/non-TIM mode conversion and conversion between different types ofBSS mode.

FIG. 6 illustrates a format of an operating mode notification elementaccording to an exemplary embodiment.

Referring to FIG. 6, an AH operating mode notification element 600 mayinclude an operating mode field 610.

The operating mode field 610 has the same value as an operating modefield of the AH operating mode notification frame. The AH operating modenotification element may be included in a beacon, an associationrequest, an association response and a probe response and be used forthe STA to notify the AP of the operating mode of the STA when the STAfirst enters the BSS and also used for the AP to notify the STA of theoperating mode of the AP.

The AH operating mode notification frame may be used for the STA tonotify a particular AP of a change of the operating mode of the STA,maintaining association with the AP after the STA is associated with aparticular AP, or be used for the AP to notify STAs associated with theAP of a change of the operating mode of the AP.

The operating mode fields 610 of the AH operating mode notificationelement and the AH operating mode notification frame may be defined asin 620 or 630 in FIG. 6. The configurations defined in 620 and 630 areprovided for illustrative purposes only, and a frame in a differentformat including similar information may be also used, with differentfield lengths and orders.

Two bits following channel widths 621 and 631 may be interpreteddifferently in transmission from the AP to the STA from in transmissionfrom the STA to the AP.

The operating mode field format 620 transmitted from the AP to the STAmay include the channel width 621 indicating information on a channelbandwidth used by the AP, a BSS mode 621 indicating information on a BSSmode, a number of spatial streams Rx Nss 625 indicating a number ofspatial streams received by the AP, and an Rx Nss type 627 indicatinginformation on an Rx Nss type.

The operating mode field format 630 transmitted from the STA to the APmay include the channel width 631 indicating information on a channelbandwidth used by the STA, a Require TIM 633 indicating information on aTIM mode that the STA requires to change, a Reserved 635 indicating anundefined field for further availability, a number of spatial streams RxNss 637 indicating a number of spatial streams received by the STA, andan Rx Nss type 639 indicating information on an Rx Nss type.

The channel width 621 and the channel width 631 may indicate theinformation on the channel bandwidths supported by the AP and the STA.

Hereinafter, functions and illustrative values of the respective fieldsare described regardless of reference numerals of the fields.

<Channel Width>

Channel width values may be defined as in Table 1.

TABLE 1 Set to 0 for 1 MHz Set to 1 for 2 MHz Set to 2 for 4 MHz Set to3 for 8 MHz Set to 4 for 16 MHz Set to 5 to 7: Reserved

<Rx Mss>

If the Rx Nss Type subfield is 0, Rx Nss indicates the maximum number ofspatial streams that the STA can receive. If the Rx Nss Type subfield is1, Rx Nss indicates the maximum number of spatial streams that the STAcan receive as a beamformee in an SU PPDU using a beamforming steeringmatrix derived from a VHT Compressed Beamforming report with FeedbackType subfield indicating MU in the VHT Compressed Beamforming frame(s).

Rx Nss values may be defined as in Table 2.

TABLE 2 Set to 0 for Nss = 1 Set to 1 for Nss = 2 Set to 2 for Nss = 3Set to 3 for Nss = 4

<Rx Nss Type>

If the Rx Nss Type is 0, the Rx Nss subfield may indicate a maximumnumber of spatial streams that the STA can receive. If the Rx Nss Typeis 1, Rx Nss indicates the maximum number of spatial streams that theSTA can receive as a beamformee in an SU PPDU using a beamformingsteering matrix derived from a VHT Compressed Beamforming report withFeedback Type subfield indicating MU in the VHT Compressed Beamformingframe(s).

<BSS Mode>

The BSS Mode may be used to report the BSS mode of the AP.

A BSS may be operated in a form of a mixed mode BSS supporting all STAs,sensor only BSS supporting sensor nodes only, or offloading only BSSsupporting offloading devices only. Field values to distinguish the BSSmodes may be defined as in Table 3.

TABLE 3 Set to 0 for Sensor only BSS Set to 1 for Offloading only BSSSet to 2 for Mixed Mode BSS 3: Reserved (extendable to further supportdifferent types of BSS)

When STAs associated with the AP during operation in a mixed mode BSSare all sensor nodes or offloading STAs, the AP may change the operationmode of the AP to the sensor only BSS or offloading only BSS. In thechanged mode, a frame and a protocol sequence optimized for the mode maybe used to minimize communication overhead.

To change to the mixed mode BSS from operation in the sensor only BSS oroffloading only BSS so as to support various devices, the AP may verifycapability of an STA currently in association, and change to the mixedmode BSS only when all STAs currently in association with the AP areable to operate.

<Require TIM>

A sensor node may select an operation mode not involving verification ofa TIM even without listening to a beacon in order to save power for along time. The STA, which is operating in the non-TIM operation mode notinvolving verification of a TIM, may need to change to the TIM operationmode as an operation mode involving verification of a TIM of a beacon incase of emergency or a request for bursty traffic transmission.

Also, the STA may need to change from the TIM operation mode to thenon-TIM operation mode, for example, when power is needed. To supportthe change of the TIM operation, maintaining association, the STA maynotify the AP of the operation mode using a Require TIM bit. The changeof the operation mode is reported, for instance, as follows.

Set to 1 for STA to operate in TIM Operation

Set to 0 for STA to operate in non-TIM Operation

When the STA changes the operation mode between the TIM operation modeand the non-TIM operation mode, an operation pattern of the STA, such asa listen interval and a wakeup interval of the STA, may change. Thus,the AP changes a group for the STA based on the operation pattern of theSTA changed on the change of the operating mode so that the STA belongsto a different group of STAs having similar operation patterns in orderto optimize BSS management, reallocate an AID for the STA, and changethe power save parameters of the STA, such as the listen interval andthe wakeup interval.

When the TIM operation mode of the STA is changed, the AP may perform achange of the group of the STA and AID reallocation and notify the STAof changed operating information on the STA using an operating modechange response frame including the changed operating information, forexample, reallocated AID information. Further, the operating mode changeresponse may further include power save parameters of the STA properlychanged for the change of the TIM operation mode or group reallocationfor the STA, for example, a listen interval, a sleep duration, or awakeup interval.

FIG. 7 illustrates a configuration of an action field format of anoperating mode change request frame according to an exemplaryembodiment.

A mode change method using an operating mode notification frame and amode change method using an AH operating mode change request and an AHoperating mode change response may be used simultaneously.

An Operating Mode Change Request field may include information neededfor the STA to make a request for an operating mode change to the AP.

The Operating Mode Change Request field may include a request of the STAfor a TIM/non-TIM operation mode change and a request of the STA for achange of power save parameters including sleep interval information,such as a listen interval, a maximum idle period, a WNM-sleep intervalor a wakeup interval.

The Operating Mode Change Request field may also include sectorallocation request information, for example, a group number or ID of anoptimal sector to which the STA wishes to belong, and traffic typeinformation on the STA for reference for the AP to reallocate an AID tothe STA, for example, estimated amount of traffic of the STA,periodicity of the traffic and whether the STA conducts uplink-orientedtransmission or down-oriented transmission.

In addition, the Operating Mode Change Request may include service typeinformation on the STA, for example, information on whether the STA is asensor node sleeping for a long time, a sensor node comparativelyfrequently waking up, a sensor node waking up event-driven orperiodically, an offloading device, a device using a streaming service,or a device using a VoIP service.

FIG. 8 illustrates a configuration of the Operating Mode Change Requestfield according to an exemplary embodiment.

Referring to FIG. 8, an operating mode change request frame 800 mayinclude Mode Change Control field 810 and Power Saving Parameters 820.

Mode Change Control field 810 may include a Require TIM 811, a Change PSParameter 813 and a Presence of other subfields 815.

Power Saving Parameters 820 may indicate requested changes of power saveparameters, such as a listen interval, a maximum idle period or sleepinterval information of the STA including a WNM-sleep interval or awakeup interval.

Other subfields or Other optional Sub elements may include traffic typeinformation on the STA for reference for the AP to reallocate an AID ofthe STA, for example, estimated amount of traffic of the STA,periodicity of the traffic and whether the STA conducts uplink-orientedtransmission or down-oriented transmission.

Further, Other subfields may include service type/device typeinformation on the STA, for example, information on a battery-poweredsensor node or a sensor node connected to a power source, abattery-powered notebook or a notebook connected to a power source, asensor node sleeping for a long time, a sensor node comparativelyfrequently waking up, a sensor node waking up event-driven orperiodically, an offloading device, a device using a streaming service,or a device using a VoIP service.

Other subfields may also include sectorization information, for example,optimal sector selection information including a sector group ID orsector ID, the optimal sector selection information as information forselection of an optimal sector to which the STA wishes to be allocatedbeing discovered by the STA through a sector beacon/NDP type discoveryframe of the AP and being reported by the STA to the AP forsectorization of the STA.

Mode Change Control field 810 may indicate whether the STA wants the TIMoperation or the non-TIM operation and whether the operating mode changerequest frame includes a request for a change of power save parameters,such as a listen interval change, a maximum idle period change, aWNM-sleep interval change, or a wakeup interval change.

Operating Mode Change Request field may include information on a traffictype, device type or service type of the STA. Also, the Operating ModeChange Request field may include information on a request of the STA forsector allocation or sector change.

FIG. 9 illustrates different configurations of an operating mode changerequest frame according to an exemplary embodiment.

Referring to FIG. 9, an Operation Mode Change Request field 900 of an AHoperating mode change request frame may be divided into fields 910, 920and 930 including information on a request for an operating mode changeand an Optional sub elements field 940 corresponding to Order 4 of FIG.7.

When a change of a power save parameter of the STA is needed due to achange in an operational environment, the STA may request the change ofthe power save parameter to the AP through an operating mode changerequest frame.

The STA may indicate a changed listen interval value in a ListenInterval field. As the listen interval value is greater, the AP maybuffer a frame for the STA for a longer time and the STA may maintainthe sleep state for a longer time.

The STA may request a change of a maximum idle period to the AP using aMax Idle Period field and an Idle Options field.

The STA may request a change of a sleep interval such as a WNM-sleepinterval or wakeup interval if the STA wishes to, and a changedWNM-sleep interval value or wakeup interval value may be indicated in aWNM-Sleep Interval field or Wake Up Interval field.

The Operation Mode Change Request field 900 may include only oneinformation among the listen interval, the maximum idle period and theWNM-sleep interval or wakeup interval.

Alternatively, the Operation Mode Change Request field 900 may include acommon value to represent a plurality of interval values. For example, asleep interval value field may have a representative value a, and thelisten interval, the maximum idle period and the WNM-sleep interval orwakeup interval may be obtained by multiplying a by a preset constant.

For instance, the AP may establish rules in the BSS, such as Listeninterval=100*a, Max idle period=10000000*a, and WNM-Sleep Interval orWake Up Interval=1000*a. Here, the STA may indicate the value a in powersave parameter information of the Operation Mode Change Request field totransmit to the AP, and the AP may obtain the listen interval, themaximum idle period and the WNM-sleep interval or wakeup interval bymultiplying a by a preset constant.

When the STA wishes to transfer to a particular STA group, the STA mayexplicitly indicate an ID of a desired STA group in an STA Group IDfield. The STA group may be implicitly determined by an AID allocatedfor the STA group in the BSS, and in this case, the STA Group ID fieldmay not need using.

A Device type or Service type field may include information on a devicetype or a service type used by a device for reference in AIDreallocation of the STA.

Other subfields may include sectorization parameters, such asinformation on a sector group desired by the STA, for example, a sectorgroup ID and a sector ID, which may be used for reference when the APallocates a sector for the STA or changes a sector of the STA.

A Mode Change Control field 910 may include any one of a first format950, a second format 960 and a third format 970.

<Details of Subfields of First Format 950>

When the STA wants a TIM operation, the STA may set a Require TIM bitto 1. When the STA wants a non-TIM operation, the STA may set theRequire TIM bit to 0.

When the Require TIM bit of the STA is different from that in a previousSTA mode, for example, when the STA wishes to change from the non-TIMoperation to the TIM operation by setting the Require TIM bit to 1, theAP may perform AID reallocation, group reallocation and slotreallocation in connection with the change of the TIM operation mode ofthe STA.

When Change Listen Interval is set to 1, a Change Listen Interval fieldindicates that the STA wishes to set a listen interval to a differentvalue from previous one. When Change Listen Interval is set to 1, ListenInterval of the operating mode change request frame 900 necessarilyincludes a listen interval value.

A Change Listen Interval field being 0 indicates that the STA may notwish to change the listen interval. Here, the STA does not set thelisten interval, and the AP may not need to refer to the listen intervalof the Operating Mode Change Request field.

Even though Change Listen Interval is set to 0 as the STA does not wishto change the listen interval, the AP may change the listen interval ofthe STA and notify the STA of the changed listen interval when the APtransmits the operation mode change response if determining that thechange is needed.

Change Max Idle Period set to 1 indicates that the STA wishes to set amaximum idle period to a different value from previous one. When ChangeMax Idle Period is set to 1, the Operating Mode Change Request fieldnecessarily includes a Max Idle Period subfield and an Idle Optionssubfield which are set to corresponding values.

Change Max Idle Period set to 0 indicates that the STA does not wish tochange the maximum idle period. The STA does not set the Max Idle Periodsubfield and the Idle Options subfield, and the AP may not need to referto the Max Idle Period subfield and the Idle Options subfield.

Even though Change Max Idle Period is set to 0 as the STA does not wishto change the maximum idle period, the AP may change the maximum idleperiod of the STA and notify the STA of the changed maximum idle periodwhen the AP transmits the operation mode change response if determiningthat the change is needed.

Change WNM-sleep Interval or Change Wakeup Interval set to 1 indicatesthat the STA wishes to set a WNM-sleep interval or wakeup interval to adifferent value from previous one. When Change WNM-sleep Interval orChange Wakeup Interval is set to 1, Change WNM-sleep Interval or ChangeWakeup Interval of the Operating Mode Change Request field necessarilyhas a set WNM-sleep interval or wakeup interval value.

Change WNM-sleep Interval or Change Wakeup Interval set to 0 indicatesthat the STA does not wish to change the WNM-sleep interval or wakeupinterval. The STA may not set the WNM-sleep interval or wakeup interval.The AP does not refer to the WNM-sleep interval or wakeup interval ofthe Operating Mode Change Request field.

Even though Change WNM-sleep Interval or Change Wakeup Interval is setto 0 as the STA does not wish to change the WNM-sleep interval or wakeupinterval, the AP may change the WNM-sleep interval or wakeup intervaland notify the STA of the changed WNM-sleep interval or wakeup intervalwhen the AP transmits the operation mode change response if determiningthat the change is needed.

When Max Idle Period, Change WNM-Sleep Interval and WNM-Sleep Intervalor Wake Up Interval specify one common value instead of respectivevalues, three Max Idle Period, Change WNM-Sleep Interval and WNM-SleepInterval or Wake Up Interval fields may be combined into one field.

When the STA wishes to move to a particular STA group, a Grouppreference preset bit of the Mode Change Control field is set to 1 andan ID of the STA group is clearly included in STA Group ID of theOperating Mode Change Request field.

When the Group preference preset bit is 0, the AP does not refer to STAGroup ID of the Operating Mode Change Request field.

When group reallocation is needed for the STA even though the Grouppreference preset bit is 0, the AP may perform group reallocation. Here,information on the group reallocation may be transmitted to the STAusing the operating mode change response.

When the STA group is implicitly determined by the allocated AID in theBSS, the information on the group reallocation may be omitted.

Traffic or service type present may indicate information on a traffictype or service type that the AP refers to in AID reallocation or aservice type used by a device.

When power consumption information on a battery powered sensor node anda battery powered smart phone and information on a periodicallywaking-up sensor node and an event-driven waking-up sensor node areincluded, the AP may more efficiently perform AID reallocation/STAgrouping in consideration power consumption requirements and a wakeupperiod of the STA.

Part of a Reserved bit may be used to indicate presence or absence ofsectorization information including information on an STA-desired sectorgroup, for example, a sector group ID and a sector ID.

<Details of Subfields of Second Format 960>

The second format 960 may further an Access Policy subfield in additionto the subfields of the first format 950.

The Access Policy subfield may indicate a medium access method that theSTA wishes to use.

<Details of Subfields of Third Format 970>

The third format 970 includes Periodic, Direction and Traffic Typesubfields. The Periodic, Direction and Traffic Type subfields aredefined as follow for use.

The Periodic subfield indicates whether traffic of the STA is periodic.

1: Traffic is periodic

0: Traffic is aperiodic or unspecified

Direction (2 bit)

00: Uplink traffic-oriented

10: Downlink traffic-oriented

01: Direct link

11: Bidirectional

Traffic Type

00: AC_BE (Best Effort)-oriented

01: AC_BK (Background)-oriented

10: AC_VI (Video)-oriented

11: AC_VO (Voice)-oriented

When the AP has information on STA traffic, such as periodicity,direction (uplink-oriented or downlink-oriented), and a traffic type(video, voice, . . . ), the AP may group STAs with similar trafficcharacteristics and allocate an AID, thereby more efficiently managing aBSS.

Meanwhile, in FIG. 9, a Reserved bit may be used to indicate presence orabsence of sectorization information including information on anSTA-desired sector group, for example, a sector group ID and a sectorID.

A reference numeral 980 of FIG. 9 illustrates a configuration ofsubfields of Optional sub elements 940.

When the STA wishes to change a bandwidth or Nss, transmitting theoperating mode change request frame, an Operating mode notificationelement 981 may be inserted into an Optional sub elements 940.

A TPSEC element 983 may be configured in a format shown in FIG. 12.

Other fields 985 may be used when additional information is needed.

Power Save related element 985 may be used to indicate an elementincluding additional information on power saving.

The STA may transmit information on a preferred wakeup time, a preferredwakeup duration and a wakeup interval of the STA inserted into PowerSave related element 985 to the AP. The AP may utilize the informationincluded in Power Save related element 985 in STA grouping and AIDallocation and report an actually allowed wakeup time, wakeup durationand wakeup interval of the STA through the operating mode changeresponse.

The STA may transmit operating mode information to the AP not only in amode change after association but also in association with the AP, sothat the operating mode information may be used to set up an initialoperation mode of the STA. When the STA transmits desired operating modesetup information to the AP in first association with the AP, the AP mayutilize the operating mode setup information in initial grouping/AIDallocation of the STA. To this end, the aforementioned medium accesspreference element including information similar to the operation modechange information of the STA included in the operating mode changerequest frame may be used. The STA transmits, to the AP, an associationrequest frame including a medium access preference element inassociation with the AP, and the AP determines whether to allowassociation of the STA based on the medium access preference element,and transmits, to the STA, operating mode information allowed for theSTA to be included in a medium access parameter element of anassociation response frame if the association is allowed.

Since the information included in the medium access preference elementis substantially similar to the information of the Operating Mode ChangeRequest field of the operating mode change request frame, the STA mayinclude an Operating Mode Request field in the association request frameas a form of an information element (IE), instead of the medium accesspreference element, in the association request.

The medium access preference element may have a configuration shown inFIG. 14.

FIG. 10 illustrates a use of the Access Policy subfield of FIG. 9. FIG.11 illustrates another use of the Access Policy subfield of FIG. 9.

The Access Policy subfield may illustrate a medium access method used bythe STA. For example, when the Access Policy subfield uses three bits,each bit may be defined as in FIG. 10.

A first bit means use of enhanced distributed channel access (EDCA), asecond bit means use of hybrid coordinator function (HCF) controlledchannel access (HCCA), and a third bit means use of channel access ofslotted carrier sense multiple access (CSMA) newly defined in IEEE802.11ah, that is, a channel access method using RAW.

The STA sets a channel access method to use to 1 (a plurality of channelmethods may be adopted), and the AP may use the channel access method ofthe STA in STA grouping, AID allocation and slot allocation. Forexample, when the STA does not support a slotted method, the AP mayallocate the STA to another STA group and may not allocate a slot to theSTA.

When a different channel access method is defined other than the slottedmethod defined in the WLAN system, four bits illustrated in FIG. 4 maybe used. When an additional channel access method is supported,definition of a bit may be extended in the same manner.

FIG. 12 illustrates a TSPEC element in accordance with relatedtechnology. FIG. 13 illustrates a configuration of a TS Info field ofFIG. 12.

The Optional sub element 940 of FIG. 9 may further include elements usedfor the AP to realize the operating mode of the STA in detail and toeffectively allocate a group and an AID for the STA or set up a powersave parameter.

For example, the Optional sub element may include a TSPEC element.

The TSPEC element illustrates quality of service (QoS) required by theSTA, and the AP may conduct more efficient STA grouping and AIDallocation with reference to the QoS.

FIG. 13 illustrates the TS Info field of the TSPEC element.

Access Policy 1310 of the TS Info field is two bits, which illustratesEDCA and HCCA only. Reserved 1320 of the TS Info field may representAccess Policy of FIG. 10 or 11 using additional one to two bits.

When the TSPEC element is included in the Optional sub element and anextended access policy is used for the TSPEC element, the Access Policysubfield of the Mode Change Control field may be omitted.

FIG. 14 illustrates a configuration of the medium access preferenceelement described above.

Fields, such as Access Policy subfield, Periodic, Direction and TrafficType, included in an Access Preference field 1410 of the medium accesspreference element 1400 are equivalent to the fields with the same namesillustrated in FIG. 9.

The STA may transmit the medium access preference element 1400 to beincluded in an association request frame to the AP. The AP may properlyperform initial grouping and AID allocation for the STA in associationof the STA with reference to the TIM operating mode, an access policyand a traffic type of the STA.

Access Preference field 1410 may include subfields as illustrated in areference numeral 1420.

Power save related optional element 985 illustrated in FIG. 9 may bealso included in the association request frame. A Device type or Servicetype field may illustrate a device type of the STA or a service typeused by the STA.

A request for a TIM/non-TIM operation mode may be transmitted to the APthrough the operating mode notification element or be expressed with abit allocated in the association request or with an allocated bit amongreserved bits of the Access Preference field 1420.

The medium access preference element may include sectorizationparameters, such as STA preferred sector information, for example, asector group ID or sector ID, which may be used for reference when theAP allocates a sector for the STA or changes a sector. The STA mayinclude sectorization information, such as STA desired optimal sectorinformation, for example, a sector group ID or sector ID, discoveredthrough a sector beacon/NDP type discovery frame, so that the AP mayallocate an optimal sector to the STA in association.

FIG. 15 illustrates an action field format of an operating mode changeresponse frame according to an exemplary embodiment.

FIG. 15 shows that an AH operating mode change response frame is definedas an action frame. The action frame may have a different format fromthat of FIG. 15 as long as it includes information used to transmit aresult of an operating mode change.

An AH operating mode change response field is used for the AP totransmit a result of a changed operating mode to the STA. The AHoperating mode change response field may report whether the AP allows arequest for the change of the TIM mode of the STA.

Further, the AH operating mode change response field notifies the STA ofan reallocated AID of the STA. When the STA requests a change of a powersave parameter, such as a listen interval, a maximum idle period and aWMN-sleep interval or wakeup interval, the AH operating mode changeresponse field may notify the STA of an actual power save parameterallowed by the AP and transmit changed operation mode information to theSTA. Further, when the STA operates in a sectorization mode, the AP mayadditionally transmit, to the STA, operation mode information on areallocated sector group for the STA, for example, a sector ID or groupID, and on a sector transmission duration.

FIG. 16 illustrates a configuration of an operation mode change responsefield according to an exemplary embodiment.

Referring to FIG. 16, the operation mode change response field 1600 mayinclude a Mode Change Result field 1610, an AID field and Power Savingparameters.

AID includes an AID value that the AP reallocates to the STA, and thePower Saving parameters illustrate an actual power save parameter valueallowed by the AP when the STA requests a change of a power saveparameter, such as a listen interval, a maximum idle period and aWNM-sleep interval or wakeup interval.

Other subfields may include sectorization information reported to theSTA in operation in a sectorization mode, such as a sector numberallocated or reallocated to the STA, a sector ID or a sector group ID, atotal number of sectors and a sector duration. Other subfields may beused to first allocate a sector to the STA or to reallocate a sector tothe STA.

Mode Change Result field 1610 may include various subfields, forexample, in a format as illustrated in a reference numeral 1620.

A Solicited/Unsolicited field illustrates whether an operating modechange response is transmitted as a response to an operating mode changerequest transmitted by the STA or is for the AP to request an operationmode change even though the STA does not make a mode change request.

TIM Mode illustrates a TIM mode of the STA allowed by the AP, forexample, a TIM operation/Non-TIM operation.

AID Changed indicates that an AID is reallocated, and may include areallocated AID value in the operating mode change response when the AIDis reallocated.

Changed PS Parameters may indicate that a power save parameter, such asa listen interval, a maximum idle period and a WNM-sleep interval or awakeup interval, is changed. When a power save parameter is allowed tobe change by the AP, the operating mode change response may include thechanged power save parameter allowed by the AP.

FIG. 17 illustrates a configuration of an operating mode change responsefield according to another exemplary embodiment.

Referring to FIG. 17, the operating mode change response field 1700 mayinclude a Mode Change Result field 1710.

An AID subfield includes an AID reallocated by the AP.

An STA Group subfield includes an STA group ID allocated by the AP. SlotNo indicates a slot number allocated to the STA when slotted CSMA isused.

When the AID of the STA is determined in the BSS, the STA group ID isimplicitly determined When slotted channel access is managed in a methodof separately reporting the slot number, STA Group ID and Slot No may beomitted.

Listen Interval represents a listen interval allowed by the AP for theSTA.

Max Idle Period and Idle Options represent information on a maximum idleperiod allowed by the AP for the STA.

WNM-Sleep interval or Wakeup Interval represents a WNM-sleep interval orwakeup interval allowed by the AP for the STA.

The operation mode change response field 1700 may include only one ofListen Interval, Max Idle Period and, WNM-Sleep Interval or WakeupInterval.

Alternatively, the operation mode change response field 1700 may includea common value to represent a plurality of interval values. For example,a sleep interval value field may have a representative value a, and thelisten interval, the maximum idle period and the WNM-sleep interval orwakeup interval may be obtained by multiplying a by a preset constant.

For instance, the AP may establish rules in the BSS, such as Listeninterval=100*a, Max idle period=10000000*a, and WNM-Sleep Interval orWake Up Interval=1000*a. Here, the AP may indicate the value a in powersave parameter information of the Operation Mode Change Response fieldto transmit to the STA, and the STA may obtain the listen interval, themaximum idle period and the WNM-sleep interval or wakeup interval bymultiplying a by a preset constant.

Other subfields may include sectorization information reported to theSTA in operation in a sectorization mode, such as a sector numberallocated or reallocated to the STA, a sector ID or a sector group ID, atotal number of sectors and a sector duration. Other subfields may beused to first allocate a sector to the STA or to reallocate a sector tothe STA.

A Mode Change Result field 1710 may include various subfields, forexample, in a format as illustrated in a reference numeral 1730.

Solicited/Unsolicited set to 1 may represent Unsolicited. In a statethat the AP does not explicitly receive an operating mode change requestfrom the STA, the AP may use an unsolicited response when the APreallocates an STA group, reallocates an AID of the STA and changes anSTA group considering a current condition of the BSS, for example, thatadditionally divided groups are needed as a great number of particularSTAs join the AP or that a number of groups needs to decrease as a greatnumber of STAs leave the BSS.

Solicited/Unsolicited set to 0 may represent solicited. Here,Solicited/Unsolicited represents a response to an operating mode changerequest. When the STA requests a mode change to the AP using anoperating mode notification frame, the AP may respond using a solicitedoperating mode change response.

<TIM Mode>

TIM Mode represents a TIM operation mode allowed for the STA. When theAP allows a request for a non-TIM operation or TIM operation made by theSTA, a TIM operation (set to 1) or non-TIM operation (set to 0) bit maybe set up.

When the request is not allowed so that a different TIM operation modefrom requested by the STA is set up, for example, when the STA requeststhe non-TIM operation but the AP does not support the non-TIM operationand thus sets up the TIM operation, the STA accords follows the TIMoperation mode set up by the AP. When the STA is allowed to request aTIM mode change only with respect to a TIM mode supported by the AP, theSTA requests the TIM mode change only when the AP supports the TIM mode,and thus a TIM mode request by the STA may be always accepted by the AP.In this case, a TIM mode subfield is not used, so that a one bit-reducedframe format may be designed.

<AID Changed>

AID Changed is set to 1 when the AP changes an AID. When an AID Changedbit is set to 1, the Operating Mode Change Response field necessarilyincludes an AID subfield with a valid AID set.

When the AP does not change an AID of the STA, an original AID of theSTA may be included in the AID subfield and transmitted. In this case,the AID Changed bit may be omitted.

Group ID Changed is set to 1 when the AP changes an STA group of theSTA. When a Group ID Changed bit is set to 1, the Operating Mode ChangeResponse field necessarily includes an STA Group ID subfield with avalid Group ID set. When slotted channel access is operated in a mannerof implicitly determining an STA Group ID when the AID of the STA isdetermined in the BSS, Group Changed may be omitted.

Listen Interval Changed is set to 1 when the AP changes a listeninterval of the STA. Here, a Listen Interval field includes a listeninterval value allowed by the AP.

Max Idle Period Changed is set to 1 when the AP changes a maximum idleperiod of the STA. Here, Max Idle Period and Idle Options subfieldsinclude a value allowed by the AP.

WNM-Sleep Interval Changed or Wake Up Interval Changed is set to 1 whenthe AP changes a WNM-sleep interval or a wakeup interval of the STA.Here, a WNM-Sleep Interval or Wake Up Interval field includes aWNM-sleep interval or wakeup interval value allowed by the AP.

Other subfields 1720 may indicate that a sector is allocated orreallocated to the STA. In this case, Other subfields may includesectorization parameter, such as a sector number allocated orreallocated to the STA, a sector ID or a sector group ID, a total numberof sectors and a sector duration. Other subfields may be used to firstallocate a sector to the STA or to reallocate a sector to the STA.

Optional sub elements 1720 may include an element including additionalinformation on power saving. When the STA transmits the elementincluding the additional information on power saving as in 985 of FIG.9, inclusive of a preferred wakeup time, a preferred wakeup duration anda wakeup interval of the STA, transmitting an operating mode changerequest, the AP may use the element in grouping and AID allocation forthe STA and transmit an actual wakeup time, an actual wakeup durationand an actual wakeup interval allowed for the STA to be included inOptional sub elements of an operating mode change response to the STA.

When the AP receives the association request including the medium accesspreference element 1400 of FIG. 14 from the STA, the AP may respond tothe STA with the association response including the medium accessparameter element of FIG. 18 or 19. By transmitting the associationresponse frame including the medium access parameter element to the STA,the STA may set up an initial operating mode in the BSS. The mediumaccess parameter element is an element including similar information tooperation mode change information of the STA included in the operatingmode change response frame allowed by the AP. When the medium accessparameter element is included in the association response, the STA mayrecognize a TIM mode of the STA allowed by the AP at association time,an AID of the STA, power save parameters including a sleep duration,such as a listen interval or wakeup interval, an allocated sector groupof the STA, such as a sector ID or sector group ID, and durationinformation on a relevant sector if the STA uses sectorization, andimmediately set up an operating mode at association time based on theelement.

Since the information included in the medium access parameter element issubstantially similar to the information of the Operating Mode ChangeResponse field of the operating mode change response frame, the STA mayinclude an Operating Mode Response field in the association responseframe as a form of an IE, instead of the medium access parameterelement, in the association response.

FIG. 18 illustrates a configuration of a medium access parameter elementaccording to an exemplary embodiment. FIG. 19 illustrates aconfiguration of a medium access parameter element according to anotherexemplary embodiment.

The medium access parameter element 1800 may include a medium accessparameter control subfield 1810. The medium access parameter controlsubfield 1810 may include various subfields as in 1830.

TIM Mode represent a TIM operation mode supported by the AP. When the APallows a request for a non-TIM operation or TIM operation made by theSTA, a TIM operation (set to 1) or non-TIM operation (set to 0) bit maybe set up.

Listen Interval Accepted set to 1 means that a listen interval requestedby the STA is accepted by the AP. Here, the STA may not refer to ListenInterval of the medium access parameter element.

Max Idle Period Accepted set to 1 means that a maximum idle periodrequested by the STA is accepted by the AP. In this case, the STA maynot refer to Max Idle Period and Idle options of the medium accessparameter element.

WNM-Sleep Interval Accepted or Wake up interval Accepted set to 1 meansthat a WNM-sleep interval requested by the STA is accepted by the AP. Inthis case, the STA may not refer to WNM-Sleep Interval or Wake upinterval of the medium access parameter element.

When Listen Interval Accepted, Max Idle Period Accepted and WNM-SleepInterval Accepted or Wake up interval Accepted are not 1, which meansthat the AP set different values from requested by the STA, values setby the AP are verified with reference to relevant subfields.

When the STA operates in a sectorization mode, the AP may furthertransmit, to the STA, sectorization related operation mode information,for example, a reallocated sector group of the STA, such as a sector IDor group ID, and a sector transmission duration, included in OtherSubfield of the medium access parameter.

FIG. 19 illustrates a medium access preference element without a MediumAccess Parameter Control subfield of FIG. 18.

In this instance, acceptance of a TIM mode requested by the STA may beindicated by allocating another bit of an association response or beidentified through an error code of the association response.

FIG. 20 illustrates a schematic configuration of an AP according to anexemplary embodiment.

Referring to FIG. 20, the AP 2000 includes a reception unit 2010, acontroller 2020 and a transmission unit 2030.

The reception unit 2010 receives an operating mode notification frameincluding information on a bandwidth used by an STA, information on anumber of used spatial streams and information on a change of a TIMmode.

The reception unit 2010 may receive an operating mode change requestframe including the information on the change of the TIM mode of theSTA, a request for a change of a power save parameter and information ona change of a service type of the STA.

The controller 2020 determines whether to allow the change of the TIMmode of the STA. Further, the controller 2020 determines whether tochange the TIM mode of the STA and whether to change the power saveparameter. In addition, the controller 2020 determines a group changefor the STA and AID reallocation based on the change of the TIM mode ofthe STA, the change of the power save parameter of the STA and theinformation on the service type of the STA.

The transmission unit 2030 transmits, to the STA, an operating modechange response frame including information on a reallocated AID of theSTA.

Also, the transmission unit 2030 transmits, to the STA, an operatingmode change response frame including at least one of information on aTIM mode allowed by the AP 2000, a changed power save parameter of theSTA allowed by the AP 2000, information on the reallocated AID by the AP2000 and allocation information on a sectorization group for the STAallocated or reallocated by the AP 2000.

FIG. 21 illustrates a schematic configuration of an STA according to anexemplary embodiment.

Referring to FIG. 21, the STA 2100 includes a reception unit 2110, acontroller 2120 and a transmission unit 2130.

The transmission unit 2130 transmits, to the AP, an operating modenotification frame including information on a used bandwidth,information on a number of used spatial streams and information on achange of a TIM mode.

Further, the transmission unit 2130 transmits, to the AP, an operatingmode change request frame including information on a change of a TIMmode of the STA, information on a request for a change of a power saveparameter and information on a change of a service type.

The reception unit 2110 receives, from the AP, an operating mode changeresponse including information on a reallocated AID.

Also, the reception unit 2110 receives, from the AP, an operating modechange response frame including at least one of information on a TIMmode allowed by the AP, information on a power save parameter of the STAallowed by the AP, information on the reallocated AID by the AP 2000 andallocation information on a sectorization group for the STA allocated orreallocated by the AP 2000.

The controller 2120 performs the change of the TIM mode based on theinformation included in the operating mode change response frame.

Further, the controller 2120 may perform a change of at least one of theTIM mode and the power save parameter based on the information includedin the operating mode change response frame.

Here, the reception unit 2110 receives, from the AP, the operating modenotification frame of the AP including information on a change of anoperating mode of the AP, and the controller 2120 may communicate withthe AP based on the operating mode notification frame of the AP.

The methods according to the exemplary embodiments may be recorded incomputer-readable media as program instructions to be implemented byvarious computers. The media may also include, alone or in combination,the program instructions, data files, data structures, and the like. Themedia and program instructions may be those specially designed andconstructed for the purposes of the present invention, or they may be ofthe kind well-known and available to those having skill in the computersoftware arts. Examples of computer-readable media include magneticmedia such as hard disks, floppy disks and magnetic tape; optical mediasuch as CD ROM disks and DVDs; magneto-optical media such as flopticaldisks; and hardware devices that are specially configured to store andperform program instructions, such as read-only memory (ROM), randomaccess memory (RAM), flash memory, and the like. Examples of programinstructions include both machine code, such as produced by a compiler,and higher level code that may be executed by a computer using aninterpreter. The described hardware devices may be configured to act asone or more software modules in order to perform the operations of theabove-described exemplary embodiments, or vice versa.

While a few exemplary embodiments have been shown and described withreference to the accompanying drawings, it will be apparent to thoseskilled in the art that various modifications and variations can be madefrom the foregoing descriptions. For example, adequate effects may beachieved even if the foregoing processes and methods are carried out indifferent order than described above, and/or the aforementionedelements, such as systems, structures, devices, or circuits, arecombined or coupled in different forms and modes than as described aboveor be substituted or switched with other components or equivalents.

Thus, other implementations, alternative embodiments and equivalents tothe claimed subject matter are construed as being within the appendedclaims.

1. An operating mode change method of a wireless local area network(WLAN) system, the method comprising: transmitting, by a station (STA)to an access point (AP), an operating mode notification frame comprisinginformation on a used bandwidth, information on a number of spatialstreams, and information on a change of a traffic indication map (TIM)mode; receiving, from the AP, an operating mode change response framecomprising information on a reallocated association identification (AID)of the STA; and performing the change of the TIM mode based on theinformation included in the operating mode change response frame.
 2. Themethod of claim 1, wherein the operating mode change response framefurther comprises group change information by the change of the TIM modewhen the change of the TIM mode is approved by the AP.
 3. The method ofclaim 1, wherein the operating mode change response frame comprises theAID reallocated by the AP due to the change of the TIM mode and achanged power save parameter corresponding to a listen interval or awakeup interval of an STA readjusted by the AP when the TIM mode changeis approved by the AP.
 4. The method of claim 1, wherein the TIM modecomprises an operation mode that does not involve verification of a TIMtransmitted from the AP and an operation mode that involves verificationof the TIM transmitted from the AP at a preset time.
 5. The method ofclaim 1, further comprising receiving, from the AP, an operating modenotification frame of the AP comprising information on a change of anoperating mode of the AP before the transmitting of the operating modenotification frame to the AP or after the performing of the change ofthe TIM mode.
 6. The method of claim 5, wherein the operating modenotification frame of the AP comprises information on whether the APsupports all kinds of STAs, supports only a sensor node or supports onlyan offloading device.
 7. The method of claim 5, wherein the operatingmode notification frame of the AP comprises information on a basicservice set (BSS) type supported by the AP, and the BSS type comprisesat least one of a sensor mode, an offloading mode, and a mixed mode. 8.An operating mode change method of a wireless local area network (WLAN)system, the method comprising: transmitting, by a station (STA) to anaccess point (AP), an operating mode change request frame comprising atleast one of information on a change of a traffic indication map (TIM)mode, information on a request for a change of a power save parameter,and information on a change of a service type of a terminal (STA);receiving, from the AP, an operating mode change response framecomprising information on a changed operating mode of the STA allowed bythe AP; and performing at least one of the change of the TIM mode andthe change of the power save parameter based on the information includedin the operating mode change response frame.
 9. The method of claim 8,wherein the operating mode change request frame further comprises atleast one of information on a request for allocation of a sectorsupported by the AP, information on a traffic type of the STA, andinformation on a service type of the STA.
 10. The method of claim 8,further comprising receiving, from the AP, an operating mode changeresponse frame comprising information on a change of an operating modeof the AP before the transmitting of the operating mode change requestframe to the AP or after the performing of the change.
 11. The method ofclaim 8, wherein the operating mode change response frame furthercomprises at least one of an allowed TIM mode, a reallocated associationidentification (AID) of the STA, information on a changed power saveparameter, and information on a group change by the change of the TIMmode.
 12. The method of claim 8, wherein the information on the requestfor the change of the power save parameter comprises at least one ofinformation on a request for a change of a listen interval of the STA,information on a request for a change of a maximum idle period, andinformation on a request for a change of a wireless network management(WNM) sleep interval or wakeup interval.
 13. The method of claim 8,wherein sector operating mode information corresponding to informationon a sector group of the STA reallocated by the AP (a reallocated sectorID or sector group ID), and a sector transmission duration are provided,when the STA operates in sectorization.
 14. The method of claim 8,wherein when the STA makes a request for association with the AP, theinformation included in the operating mode change request frame isincluded in the request for association and transmitted to the AP torequest setup of an operating mode at a time when the STA is associatedwith the AP.
 15. The method of claim 8, wherein when the AP receives anassociation request included in the operating mode change request framefrom the STA, the AP determines whether to associate with the STA, andtransmits an association response included in the operating mode changeresponse frame to the STA, if association is allowed, so that the STAsets up the operating mode at a time of association.
 16. The method ofclaim 14, wherein operating setup request information included in therequest for association comprises a TIM mode desired by the STA, a powersave parameter including a sleep duration corresponding to a listeninterval or a wakeup interval, a traffic type or a service type of theSTA, and a sector ID of a desired sector.
 17. The method of claim 15,wherein operating setup response information included in the associationresponse comprises a TIM mode allowed by the AP for the STA, an AID ofthe STA, a power save parameter including a sleep duration correspondingto a listen interval or wakeup interval, a sector group allocated forthe STA corresponding to a sector ID or sector group ID, and durationinformation on a sector when the STA uses sectorization.
 18. Anoperating mode change method of a wireless local area network (WLAN)system, the method comprising: receiving, by an access point (AP), anoperating mode notification frame comprising information on a bandwidthused by a station (STA), and information on a change of a trafficindication map (TIM) mode of the STA; determining whether to allow thechange of the TIM mode of the STA; transmitting, to the STA, anoperating mode change response frame comprising information on areallocated association identification (AID) of the STA; and receivingan acknowledgement (ACK) frame from the STA.
 19. An operating modechange method of a wireless local area network (WLAN) system, the methodcomprising: receiving, an access point (AP), an operating mode changerequest frame comprising at least one of information on a change of atraffic indication map (TIM) mode of a station (STA), information on arequest for a change of a power save parameter, and information on achange of a service type of the STA; determining whether to change theTIM mode of the STA and whether to change the power save parameter;transmitting, to the STA, an operating mode change response framecomprising information on a TIM mode allowed by the AP; and receiving anacknowledgement (ACK) frame from the STA.
 20. A station (STA) of awireless local area network (WLAN) system, the STA comprising: atransmission unit to transmit, to an access point (AP), an operatingmode notification frame comprising information on a used bandwidth,information on a number of spatial streams, and information on a changeof a traffic indication map (TIM) mode; a reception unit to receive,from the AP, an operating mode change response frame comprisinginformation on a reallocated association identification (AID) of theSTA; and a controller to perform the change of the TIM mode based on theinformation included in the operating mode change response frame. 21.The STA of claim 20, wherein the operating mode change response framefurther comprises group change information by the change of the TIM modewhen the change of the TIM mode is approved by the AP.
 22. The STA ofclaim 20, wherein the TIM mode comprises an operation mode that does notinvolve verification of a TIM transmitted from the AP and an operationmode that involves verification of the TIM transmitted from the AP at apreset time.
 23. The STA of claim 20, wherein the reception unitreceives, from the AP, an operating mode notification frame of the APcomprising information on a change of an operating mode of the AP, andthe controller performs communication with the AP based on the operatingmode notification frame of the AP.
 24. The STA of claim 20, wherein theoperating mode notification frame of the AP comprises information onwhether the AP supports all kinds of STAs, supports only a sensor nodeor supports only an offloading device.
 25. A station (STA) of a wirelesslocal area network (WLAN) system, the STA comprising: a transmissionunit to transmit, to an access point (AP), an operating mode changerequest frame comprising at least one of information on a change of atraffic indication map (TIM) mode of the STA, information on a requestfor a change of a power save parameter, and information on a change of aservice type of the STA; a reception unit to receive, from the AP, anoperating mode change response frame comprising at least one ofinformation on a TIM mode allowed by the AP, a reallocated associationidentification (AID), and information on a changed power save parameter;and a controller to perform at least one of the change of the TIM modeand the change of the power save parameter based on the informationincluded in the operating mode change response frame.
 26. The STA ofclaim 25, wherein the operating mode change request frame furthercomprises at least one of information on a request for allocation of asector supported by the AP, information on a traffic type of the STA,and information on a service type of the STA.
 27. The STA of claim 25,wherein the reception unit receives, from the AP, an operating modechange response frame comprising information on a change of an operatingmode of the AP, and the controller performs communication with the APbased on the information on the change of the operating mode of the AP.28. The STA of claim 25, wherein the operating mode change responseframe further comprises at least one of a reallocated AID of the STA,group change information by the change of the TIM mode, and a slotnumber allocated to the STA.
 29. The STA of claim 25, wherein theinformation on the request for the change of the power save parametercomprises at least one of information on a request for a change of alisten interval of the STA, information on a request for a change of amaximum idle period, and information on a request for a change of awireless network management (WNM) sleep interval or wakeup interval. 30.An access point (AP) of a wireless local area network (WLAN) system, theAP comprising: a reception unit to receive an operating modenotification frame comprising information on a bandwidth used by astation (STA), and information on a change of a traffic indication map(TIM) mode of the STA; a controller to determine whether to allow thechange of the TIM mode of the STA; and a transmission unit to transmit,to the STA, an operating mode change response frame comprisinginformation on a reallocated association identification (AID) of theSTA.
 31. An access point (AP) of a wireless local area network (WLAN)system, the AP comprising: a reception unit to receive an operating modechange request frame comprising at least one of information on a changeof a traffic indication map (TIM) mode of a station (STA), informationon a request for a change of a power save parameter, and information ona change of a service type of the STA; a controller to determine whetherto change the TIM mode of the STA and whether to change the power saveparameter; and a transmission unit to transmit, to the STA, an operatingmode change response frame comprising information on a TIM mode allowedby the AP.